On Wed, Aug 15, 2007, Francesco Pietra wrote:
>
> In my view, the worst about present implementation of divcon in antechamber
> (Amber9) is lack of keywords DUMP=int PDUMP=int SNAPGEOM as from divcon.out,
> unless they can be set (how?). This is the main need by users of antechamber
> for heavy work. Launching antechamber as in tutorial B6 is risky: if it
> crashes, all work is lost.

You are really taking the charge derivation part of antchamber where it was
not designed to go. Even it things don't crash, you would need to examine
whether or not the charge model one gets for very large molecules is a good
one.

The "am1-bcc" charge philosophy is to perform a geometry minimization on the
input molecule before assessing the charges. This makes sense for small
molecules, where geometry optimization is fast. For large, floppy molecules,
it probably makes much less sense. Again, this is a scientific question that
will require patience and research. If you wish to use divcon for this
purpose, then you should probably run it by hand, not through the antechamber
front end; then you can set whatever keywords you want.

As others have pointed out, the "divcon" program can perform either "regular"
SCF calculations, or divide and conquer ones, depending on its input.